1. Field of the Invention
The present invention relates to a spring seal device for connecting an inner tube and a tail tube in a combustor for a gas turbine etc.
2. Description of the Prior Art
FIG. 7 is a schematic cross sectional view of a prior art gas turbine combustor. Fuel, together with air from a compressor, is burnt in an inner tube 1 and a tail tube 2 provided in a turbine cylinder 6 to generate a high temperature combustion gas, which combustion gas is supplied into the turbine for driving it.
FIG. 8 is an enlarged cross sectional view of the combustor portion. As shown there, the combustor has a structure constructed by the inner tube 1 and the tail tube 2 mainly for a purpose of absorbing a thermal deformation. A spring seal 3, 4 is provided mainly for preventing air leakage from between the inner tube 1 and the tail tube 2, which spring seal is one kind of a plate spring for preventing air leakage from between the inner tube 1 and the tail tube 2 even if there occurs a thermal deformation. Said spring seal also functions to increase vibration damping of the structural system.
In FIGS. 9 to 11, a prior art seal spring portion is shown enlargedly. The spring seal is of a double structure of an outer seal plate 3 and an inner seal plate 4 in which, at an end portion of the seal plate, the inner seal plate 4 is overlapped on a cut-out portion of the outer seal plate 3, as shown in FIG. 10, so that a leakage from the cut-out portion of the outer seal plate 3 is prevented by the inner seal plate 4. Also, a stopper 9 is provided for restricting a deformation of the seal plate caused by a thermal expansion.
In the gas turbine combustor, there occurs a large differential temperature between the ordinary temperature during operation stop and a temperature of approximately 1,000.degree. C. during operation, so that a large thermal deformation occurs both in the axial direction and in the radial direction. While several tens times of starts and stops of the gas turbine are repeated, there progresses a permanent settling gradually of the spring seal which had been of a predetermined dimension at the time of inspection so as not to return to the original state and a gap is sometimes generated between the tail tube 2 and the spring seal 3, 4.
If air leaks through said gap from within the turbine cylinder into the combustor, a fuel-air ratio (ratio of fuel to air) in the combustor varies and a combustion condition varies, which often gives an unfavorable influence on NO.sub.x generation and combustion vibration.
Also, a fluid flowing through said gap causes a self-exciting vibration due to so called a clearance flow and the spring seal is caused to vibrate furiously so that there arises a fear of damage of the spring seal. And if a fraction of the spring seal plunges into the combustor, there is considered a possibility of a large accident, such as damage of turbine blades.
It is therefore an object of the present invention to provide a spring seal device for a combustor in which a spring seal for connecting an inner tube and a tail tube of the combustor is constructed so as not to cause an air leakage due to an aged deterioration thereof.